The present invention relates to a roller supporting device for supporting a roller which contacts with a mating member, particularly to a roller supporting device for preventing foreign matters from being bitten between an inner surface of the roller and a supporting shaft.
Generally, in a valve train of an engine, a valve rocker arm is provided for converting the rotary motion of a cam into the opening and closing motion of the valve. The valve rocker arm operates for performing the rocking motion along with the rotary motion of the cam, the rocking motion further causing the opening and closing motion of the valve.
Among the above valve rocker arm, some of them employ a roller as a follower which contacts the rotating cam. The roller follower mechanism is composed of a pair of supporting arms made in a fork-shape on one side of the valve rocker arm and the roller rotatably supported between the pair of supporting arms by means of the supporting shaft. In this case, both ends of the supporting shaft are fixed to the pair of supporting arms, respectively, and the roller rotates around the supporting shaft.
In the roller follower mechanism like this, from the demand on strength, a combination of a relatively hard material is used for the roller and the supporting shaft such that the roller is made of hardened steel and the supporting shaft is made of such as phosphor bronze or a brass group material, hardened steel or a surface treated material produced through such as a nitriding treatment.
The roller and the supporting shaft made of the hard material like this are in some case used in sliding contact with each other through a bearing bush, but generally used in the direct sliding contact relationship. Generally in either case, to lubricate the sliding surfaces of both the supporting shaft and the roller, it is arranged such that oil filler ports are provided for communicating with the valve rocker shaft which is the rocking center of the valve rocker arm, the valve rocker arm, the supporting arm and the supporting shaft, in order, and the lubricating oil supplied from a lubricating system of the engine is fed to the sliding surfaces of the supporting shaft and the roller through respective oil filler ports, in turn.
However, with the conventional lubricating arrangement described above, foreign matters were sometimes bitten between the sliding surfaces of the supporting shaft and the roller. The main reason of the above bite is that the lubricating oil becomes to contain foreign matters while it flows through a long oil supply passage and hence the foreign matters are conveyed to the roller follower mechanism which is the final oiling target. In other words, the lubricating oil is arranged such that it is first pumped up from an oil pan of the engine, then supplied from the oil passage within the engine block to the sliding surface between the supporting shaft and the roller through each oil filler port of the above valve rocker shaft, the valve rocker arm, the supporting arm and the supporting shaft, in order. Therefore, the distance from the oil pan to the roller follower mechanism becomes rather long and further the oil passage is narrow having a complicated form.
Since the oil filler passage of this type is processed in many case by a cutting tool such as a drill, burrs or metal particles are sometimes produced in processing. If burrs or metal particles drop due to the vibration of the engine, they are conveyed as foreign particles in the lubricating oil to the sliding surfaces of the supporting shaft and the roller which are the final oiling position of the oil supplying passage. Further, particularly in case of a diesel engine, a combustion product such as the carbon sludge is mixed in the lubricating oil, resultantly the carbon sludge entering the sliding surface between the supporting shaft and the roller.
When the foreign matters enter the sliding surface between the supporting shaft and the roller, a defect such as scuffing and/or seizure is generated in the sliding surface inducing the usual rotation of the roller, resulting in the local wear in the outer circumferential surface of the roller, and further, in the defective opening and closing movement of the valve, and in its turn, generating the poor combustion of the engine causing an abnormal sound or an unusual vibration.